[Linux-kernel-mentees] [PATCH] bpf: Fix NULL pointer dereference in __btf_resolve_helper_id()

[Peilin Ye]

Prevent __btf_resolve_helper_id() from dereferencing `btf_vmlinux`
as NULL. This patch fixes the following syzbot bug:

    https://syzkaller.appspot.com/bug?id=5edd146856fd513747c1992442732e5a0e9ba355

Reported-by: syzbot+ee09bda7017345f1fbe6@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
---
 kernel/bpf/btf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 30721f2c2d10..3e981b183fa4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4088,7 +4088,7 @@ static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn,
 	const char *tname, *sym;
 	u32 btf_id, i;
 
-	if (IS_ERR(btf_vmlinux)) {
+	if (IS_ERR_OR_NULL(btf_vmlinux)) {
 		bpf_log(log, "btf_vmlinux is malformed\n");
 		return -EINVAL;
 	}
-- 
2.25.1